Bioreactors have been used for many years for cell culture, most notably for fermentation and more recently for the growth of bacteria. These cultures are usually contained in stainless steel vessels where gas exchange, temperature, pH, dissolved oxygen levels, and circulation are closely monitored and controlled.
Photobioreactors are reactors for material that requires light. There are many designs, ranging from open-air races, to tubes, to transparent vessels. The vessels may have banks of lights around the periphery or a central core of lights. The level of control ranges from essentially none, to strict monitoring of the growth conditions. Where there is no control over the growth conditions, sterility and maintenance of cell culture purity are not considered. This may be adequate for growth of algae for biofuel production, but is not for the growth of algae as a food source. In this instance, sensors and controls, as disclosed in US Publication No. 20110136225, are employed. A bioreactor module can be connected to one or more functional modules such as a pump module, a stimulation signal generation module, a motor module, a mechanical transmission module, a gas exchange module, a temperature module, a humidity module and/or a CO2 module, among others. The bioreactor and functional modules can include standard or universal connectors to facilitate connection and movement of modules. The bioreactor system can be controlled and/or monitored by a controller that can individually identify and control each connected module and that can be adapted to collect signal data from sensors embedded in any of the modules.
The use of sensors may require special adaptations. As disclosed in US Publication No. 20110111489, a sensor adapter comprises an accommodating channel, in which the sensor can be positioned and the one end region of which is closed off by a semipermeable membrane. Moreover, the sensor adapter comprises a hollow cylindrical sealing structure, which is disposed within the accommodating channel coaxially with the longitudinal axis of the latter and with which the sensor can be disposed gas tight adjacent to the semipermeable membrane.
Processors and programmes can be used to monitor outputs from sensors and run the various controllers. As disclosed in US Publication No. 20050208473, decision making software can be used that utilizes detected changes in the course of fermentation. Decisions are aimed at determining the optima for cellular growth, optimizing for production or degradation of metabolites or substrates, or determining the limits of growth under various combinations of conditions. The invention determines optima or limits in a manner more quickly and at less cost than traditional methods. The basis for the computer generated decisions may be first or second derivative changes observed such as inflection points, limits on allowable rates of change, or the like. The most common measured parameter controlling the decision making process is the optically observed growth of the cells (e.g. microbial, animal, or plant cell cultures) under study. Any other measurable parameter (e.g. pH, temperature, pigment production) may be used to control the process (i.e., the independent variable). This process and variations of this process on a laboratory scale are valuable for research and development, education, pilot plant models, and bio-manufacturing optimization, including scale up to production volumes.